This invention relates to the field of specimen preparation, and particularly to the preparation of thin specimens for use in transmission electron microscopy.
Sample preparation is an important and time consuming requirement in the microscopy of materials. The samples required for transmission electron microscopy must be very thin, on the order of 1000 angstroms. Such specimens are extremely fragile and difficult to handle, both during the sample preparation and during the subsequent microscopy.
The principle method for producing thin specimens of non-conductive materials for examination by transmission electron microscopy is by ion beam milling. The major disadvantage of the ion thinning technique is that it is slow. For dense, fine-grained ceramics or for materials composed of elements of high atomic number, a thinning rate of about 1 um/hr is obtained. Higher rates can be achieved with special purpose, high intensity or high voltage ion beams, but usually to the detriment of specimen quality because of radiation damage or sample heating. Therefore, emphasis is placed on first producing as thin a section as possible by mechanical means in order to minimize ion milling time. For most materials, sections thinner than 75-125 um are extremely fragile and difficult to prepare mechanically. Such sections may still require several days to thin by ion miling even after extensive mechanical thinning.